Machine for drying by contact veneers obtained by peeling or slicing wood

ABSTRACT

A veneer drying machine comprises coacting endless flexible conveyor belts between which the sheets of veneer are conveyed on a path that passes between superposed pairs of heating plates. The upper of the two heating plates is vertically movable to permit movement of the coacting conveyor belts therebetween. When the upper heating plate is lowered, the conveyor belts with the veneers between them are held stationary and veneers are then dried. An overhead hood withdraws steam emitted by the hot veneer.

United States Patent Martin July 29, 1975 54] MACHINE FOR DRYING BYCONTACT 1,741,882 12/1929 Robinson 34/159 x I 0R 3,367,261 2/1968Kashiwagi... 34/162 x gigg ggg BY PEEL NG 3,418,727 12/1968 Morris34/162 x SL1 3,503,140 3/1970 Hildebrand 34/162 Jean-Marie MichelMartin, 23, rue de Turin, 75008 Paris, France Filed: Mar. 26, 1974 Appl.No.: 455,001

Inventor:

Foreign Application Priority Data Mar. 28, 1973 France 73.11060 Feb. 28,1974 France 74.06808 U.S. Cl 34/162; 34/66; 34/161 Int. Cl. F26b 9/00Field of Search 34/151, 161, 162, 62, 66,

References Cited UNITED STATES PATENTS Daly 34/162 X PrimaryExaminer-William F. ODea Assistant Examiner -Harold Joyce Attorney,Agent, or Firm-Young & Thompson [57] ABSTRACT A veneer drying machinecomprises coacting endless flexible conveyor belts between which thesheets of veneer are conveyed on a path that passes between superposedpairs of heating plates. The upper of the two heating plates isvertically movable to permit movement of the coacting conveyor beltstherebetween. When the upper heating plate is lowered, the conveyorbelts with the veneers between them are held stationary and veneers arethen dried. An overhead hood withdraws steam emitted by the hot veneer.

6 Claims, 4 Drawing Figures PATENTEU JUL 2 9 I975 SHEET mm QE Qw QmmMACHINE FOR DRYING BY CONTACT VENEERS OBTAINED BY PEELING OR' SLICINGWOOD This machine has bee'h-devisedfor putting" into application, on anindustrial and rational scale, two methods which are known and alreadyused separately in the manufacturing industry of veneers from peeled orsliced pieces of wood or timber, namely a method of contact drying andthat method particularly known in the United States of America and inCanada under the name of Tray System.

The first basic method already employed in the art consists in dryingveneers between two plates belonging to a heating press. This method hasbeen and is still utilized at the present time in a haphazard manner,either for stabilizing veneers which have already been predried or fordrying verythin veneers assembled in more or less thick stacks oralternatively for drying strong and fairly thick veneers grooved plates.l-leretofore, this method was very little used, due to the fact that aheatingplate press of known type has always proved to be ill-suited initself for the drying of veneers, especially in the usual practice ofthe manufacturing processes for veneers and plywoods.

The primary object of the invention is to provide a remedy for thesedisadvantages.

The second basic method already employed and known under the name ofTray System is directed to the mechanized taking-on load of veneers forthe purpose of storage at the outlet, for example of a woodpeeling orslicing machine for obtaining veneers in such manner as to enable thesemachines to work at their maximum speed and then to deliver the veneersthus stored to subsequent machines such as a guillotine or a continuousdrying machine.

- This method, known as the Tray System, is generally carried out by abelt conveyor comprising one or several stages, driven machanically atspeedscompati'ole both with the output of the leading machine and withthe receiving device of the machine next following.

This known installation may also be equipped with lower and upper beltsenabling the veneers to be continuously received, retained, stocked andconveyed between two conveyor belts.

This is always the case in particular for the so-called S-Tray Systemutilisable especially in conjunction in one of the methods ofconstruction of the improved machine according to the invention.

A further object of the invention is, therefore, to enable a dryingmachine to be obtained for contact drying of so-called peeled or slicedveneers, this machine being so designed as to effect this dryingoperation in substantially shorter times, with a reduced expenditure ofheat and power than in the veneer-drying methods carried out with hotair as employed up to the present time, while offering the advantage ofobtaining dry veneers which are absolutely flat, properly stabilized andhomogeneous.

This improved machine for contact drying of veneers obtained from peeledor sliced pieces of wood comprises, in combination, an assembly ofheating plates in stages, arranged in sets of two on the uprights of thesupporting frame, and between which two movable conveyor belts arecapable of performing an S circuit,

these belts being adapted to receive the veneers to 'bet dried, suppliedat the outlet of thewoodpeeling or slicing machine, one of the heatingplates o f each of these sets being so arranged as to move away from theassociated fixed heating plate, and conveyor belts in ordersimultaneously to effect the drying of the veneers by contact.

According to a particular feature of the invention, the respectiveworking faces of the heating plates in stages and arranged in sets oftwo are smooth or provided with grooves, striations of a lining.

According to another feature of the invention, each of the heatingplates, arranged so as to move away from the fixed heating plate andfrom the conveyor belts, comprises devices associated with guiding slotsformed in the uprights of the supporting frame, the fixed heatingplatesresting on members rigidly secured to these uprights.

in accordance with another characteristic feature of the invention, themachine comprises a device permitting through the intermediary of theheating plates, the application on the veneers of an effectiveadjustable pressure in identically the same way as that of a hydraulicpress comprising heating plates.

According to another feature of the invention, one of the conveyor beltsbetween which the veneers to be dried are placed when secured by theoutlet of the wood-peeling or slicing machine is formed of a woven meshof fine metal wire, the other conveyor belt being formed of a thin sheetor leaf of plastic material, these conveyor belts being driven andguided by a plurality of drums carried by the supporting frame.

According to a still further feature of the invention, the machinecomprises a plurality of conveyor belts arranged in stages and in setsof two, driven by a number of drums carried by the supporting frame,these tiered conveyor belts first moving in a zone located outside anassembly of heating plates and then between these plates which aretiered and arranged in sets of two, of which one can be slipped from thetiered conveyor belts, the veneers to be dried and the associated fixedplate, these veneers being brought between the tiered conveyor belts bya device comprising a single conveyor belt, one of the driving drums ofwhich is connected to an angularly movable arm permitting this conveyorbelt to be brought level with each set of tiered conveyor belts for thepurpose of their supply with veneers to be dried, which are collectedafter the drying operation by an identical device.

According to a still further feature of the invention, theangularly-movable arm permitting the feed of the conveyor belt supplyingthe machine with veneers to be dried, and also the mobile arm permittingthe dry veneers to be collected on the receiving conveyor belt areointly associated respectively with a guiding member made of spacedbelts made of a plastic material, the veneers being collected after thedrying operation on a conveyor belt of the same kind.

The following description, given by way of example and not in anylimitative sense, will enable the invention to be more clearlyunderstood, reference being made to the accompanying drawings, in which:

FIG. 1 shows a first embodiment of the machine for contact drying ofveneers obtained by peeling or slicing wood in accordance with theinvention;

FIG.2 shows another embodiment of this machine;

FIG. 3 is an alternative form of construction of a group of conveyorbelts;

FIG. 4 shows another alternative form of construction of machineaccording to the invention.

The machine for contact drying of veneers obtained by peeling or slicingwood shown in FIG. 1 comprises a supporting frame provided with uprights1 and 2 coupled together at their upper end by cross-members 3 and onwhich is mounted a plurality of heating plates 4 movable in height andfixed plates 5, tiered and arranged in sets of two. These platesconstitute an internal circuit through which flows a heating fluid inidentically the same way as the plates of a hydraulic press equippedwith heating plates.

The machine also comprises two conveyor belts 6 and 7 provided at theoutlet of the wood-peeling or slicing machine and intended to convey theveneers 8 to be dried towards the sets of heating plates 4 and 5, theseconveyor belts being respectively driven by drums 9 and 10 carried bybearings 11 and 12 supported by the uprights l3 and 14.

Two intermediate drums 15 and 16 are supported by bearings 17 and 18 soarranged that the conveyor belts 6 and 7 are correctly tightenedcontinuously. The conveyor belt 6 is composed of a woven mesh of finemetal wire while the conveyor belt 7 is formed either of a woven mesh offine metal wire or a thin sheet of metal or a thin sheet of plasticmaterial.

Between each set of heating plates 4 and 5, the conveyor belts 6 and 7move along a circuit of S-form by means of driving drums l9 and 20supported by bearings 21 and 22 carried by the uprights 23 and 24 whichare connected to the uprights 13 and 14 by the crossmembers 25 and 26.

The heating plates 4 are provided with studs 27 associated with guidingslots 28 formed in each of the 1 and 2 in order to enable said plates tobe slipped from the fixed plates 5 which rest on elements 29 rigidlyfixed to the uprights l and 2, and thus to be brought into a position inwhich they are applied against the veneers 8 to be dried and against thefixed plates 5, either by means of an adjustable pressure or by theirown weight.

The respective working faces of the heating plates 4 and 5 are eithersmooth or provided with grooves, striations or a lining for the samepurpose.

A suction hood 30 is arranged at the upper part of the machine in orderto permit evacuation of the steam which is evolved during the course ofthe drying operations hereforward on the veneers.

The veneers 8 to be dried are picked up at the outlet of thewood-peeling or slicing machine and brought to the conveyor belt 6 inthe direction indicated by the arrow 31, the heating plates 4 thenoccupying the position shown in FIG. 1, that is to say, they are movedapart from the veneers 8 to be dried and from the fixed plates 5.

At a definite moment, the drive of the conveyor belts is stopped andsimultaneously the heating plates 4 are lowered by virtue of the actionof the studs 27 in cooperation with the guiding slots 28, which makes itpossible to carry out contact-drying of the veneers 8. When the conveyorbelts are stopped, the veneers are held motionless between the heatingplates 4 and 5.

The plates 4 are then lifted and simultaneously the conveyor belts areagain started up in order that the veneers to be dried, which wereoutside the heating plates, may pass between the latter. At that moment,the conveyor belts are again stopped and the heating plates are oncemore lowered, the veneers thus trapped being completely dried, wherebyafter final lifting of the plates 4, the veneers are directed towards aguillotine cutting device as indicated by the arrow 32.

During the course of each veneer-drying operation,

the evacuation of the steam in the zone corresponding to the heatingplates 4 and 5 is effected through the conveyor belt 6, while theinstananeous transmission of the heat permitting the rapid discharge ofthe water contained in the veneers is effected through the conveyor belt7 and by direct contact, another portion of the heat being transmittedby the conveyor belt itself.

This machine makes it possible to reduce the drying time to aconsiderable extent due to the face that the coefficient of heattransmission is higher than that of transmission by hot air (from thebeginning to the end of the drying cycle). The temperatures which can beused are furthermore definitely higher and may even reach 200 to 300C.

The drying time thus obtained varies between 5 and 60 seconds. It may bereduced to 5 seconds for example for a veneer of walnut of 0.6 mm. inthickness, to 15 seconds for a mahogany veneer of 1 mm. in thickness,and to 20 seconds for a veneer of pine interior or poplar interior of2.5 mm. in thickness.

In the alternative form of construction shown in FIG. 2 in which theconveyor belts and the veneers to be dried move first of all in a Zonelocated outside the heating plates, the machine for contact-drying ofsocalled peeled or sliced veneers comprises, as in the previousexamples, a supporting frame including uprights 33 and 34 connected attheir upper portion by cross members 35, and on which is mounted anassembly of heating plates 36 movable in height and fixed plates 37,tiered and arranged in sets of two.

The machine also comprises a series of tiered belt conveyors arranged insets of two, each of these sets 38-39, 38a39a and 38b-39b beingassociated with one of the sets of heating plates, the conveyor beltsbeing driven by drums 40 and supported by bearings 44 and 45 carried bythe uprights 46 and 47 coupled together at their upper portion bycross-members 48.

As in the previous example, the heating plates 36 are provided withstuds 49 co-operating with guiding slots 50 provided in each of theuprights 33 and 34 in order to enable these plates to move away from thefixed plates 37 which rest on elements 51 rigidly fixed to the uprights33 and 34 and thereby to be brought, as in the previous example, to aposition in which they will apply on the veneers to be dried 52 and onthe fixed plates 37, either an adjustable pressure or the action oftheir own weight.

The veneers to be dried 52 are brought between each set of beltconveyors 38-39, 38a-39a and 3812-39!) by a single supply belt conveyor53 driven by drums of which one, 54, which is normally present in theimmediate vicinity of the drums 40, is coupled to angularly movable arm55 provided with an a slot 56 in which is engaged the shaft 57 of thisdrum also engaged in a guiding slot 58 formed in an element 59 coupledto one of the uprights 46 carrying the bearings 44 of the drums.

This machine operates in the following manner:

The veneers to be dried 52 are brought to the outlet of the wood-peelingor slicing machine-(as indicated by the arrows 60) by the supply beltconveyor 53 which may be presented, by virtue of the moving arm 55,either as shown in full lines in FIG. 2 or as drawn in broken lines at53a or at 53b in such manner as alternately to supply the veneers to bedried to the sets of conveyor belts 3839, 3811-390 and 38b39b, thecontact-drying taking place during the lowering of the heating plates 37as in the previous example.

After drying, the veneers are directed on to a single receiving conveyorbelt 61 driven by drums of which one, 62, which is normally in theimmediate vicinity of the drums 41, is coupled to an angularly-movablearm 63 identical with the arm 55, and which is provided with a slot 64in which is engaged the shaft 65 of this drum, also engaged in a guidingslot 66 formed in an element 67 coupled to one of the uprights 47carrying the bearings 43 of the drums 41, the single conveyor belt forreceiving the dry veneers being able to be presented either as indicatedin full lines in FIG. 2, or as shown in broken lines at 61a or 61b, soas to receive alternately the dry veneers coming from the sets of tieredbelt conveyors in order to direct these veneers towards a guillotinecutting device, for example, as indicated by the arrow 68.

In this way, by utilizing this form of the machine, it is possible tosupply veneers to be dried successively by means of a single beltconveyor 53 to each set of tiered conveyor belts intended to bring theseveneers between the heating plates 36 and 37. It is also possible totransfer the veneers by means of a single conveyor belt 61, afterdrying.

In this embodiment of the invention, the conveyor belts 38,38a and 38bare composed of a woven mesh of fine metal wire while the conveyor belts39, 39a and 39b are formed of a thin sheet of metal or a thin sheet ofplastic material.

A suction hood 69 is arranged at the upper portion of the machine abovethe sets of heating plates 36 and 37 in order to permit the evacuationof the steam which evolved during the drying operations of the veneers.

For the sake of clearness, there has not been shown in FIGS. 1 and 2 thealternative form in which the machine would comprise a device enablingthe application, through the intermediary of the heating plates 4 and'5and 36 and 37, on the veneers 8 and 52 to be dried, of an effectivepressure variable in identically the same manner as that of a hydraulicpress comprising heating plates of a type known per se.

There has been shown in FIG. 3 a particular arrangement of the conveyorbelts. The latter move in this case between the heating plates formed byparallel adjacent belts 70 consisting of a woven mesh of fine metal wireor a thin sheet of metal or a sheet of plastic material, the veneers tobe dried being brought on these parallel juxtaposed belts by a conveyorbelt composed of ordinary spaced-apart belts 71 of plastic material, theveneers being collected for example after drying, on a conveyor beltalso constituted by ordinary belts spaced apart, these belts 72 beingadvantageously made of plastic material.

In FIG. 4 of the drawings is shown another embodiment of the improvedmachine which involves several improvements over the aforesaidcombination.

According to a first improvement, the belt conveyors 6 and 7 asillustrated in FIG. 1 and the conveyor belts 38 and 39 as illustrated inFIG. 2 may be both made of woven metal fabric, thus permitting them bothon the two faces of the veneer to achieve adequate transmission of heatand local evacuation of steam due to the drying.

According to a second improvement, each mobile heating plate 36 of theembodiment shown in FIG. 2 may be so provided as to have a raising andlowering movement independent of the movement of the other movingplates. This means that the plate 36 of the upper tier of the dryer maybe in the raised position while the plates 36 of the lower tiers are inthe lower position. Under these conditions, the raisable conveyor belts53 and 61 assume the positions 53b and 61b, corresponding to the uppertier. The whole of this tier is in a position for conveying veneerswhile the lower tiers of the dryer are in the position for drying theveneers, with the plates 36 in their bottom position.

Under these circumstances, the assembly of the belts 53b, 38b, 39b and61b moves forward over a path equal to the length of the heating plates.The dry veneers located between the plates 36 and 37 of the upper tierare then extracted from the dryer and replaced by the same length ofmoist veneers. The plate 36 of this upper tier is then lowered so as tobegin the drying of the veneers at this tier, the two belts 53 and 61are lowered to the positions 53a and 61a and the plate 36 of this secondtier of the dryer is raised.

The entirety of the second tier thus occupies the conveying position ofthe veneers, while the other tiers, including the upper tier, are in thedrying position, and

so on. Each upper plate 36 has an independent lifting device withhydraulic or pneumatic jacks (not shown) enabling each tier to operateindependently of the others and successively.

In the embodiment shown in FIG. 4 of the drawings, there are providedtwo assemblies or stacks of plates: a first vertical stack of heatingplates 36 and 37 and a second stack of cooling plates 36a and37a. Thesecond stack of plates is absolutely identical to the first one in allrespects except for the fact that the plates 36 and 37 belonging to thefirst stack are traversed by a cooling fluid. The raising and loweringmotion of the heating plate 36 and of the cooling plate 36a of one tierare effected at the same time. They may even be fixed together with ofcourse the interposition of the heatinsulating member 73.

The fixed plates 37 and 37a of each tier may also be secured togetherwith the interposition of a heatinsulating member 73.

During the conveying period of the veneers, the heating plate 36 and thecooling plate 36a of the tier considered are therefore raised, the beltsmove forward by the length of one plate and itfollows that a length ofmoist veneers is introduced between the heating plates 36-37, a lengthof dry and hot veneer is introduced between the cooling plates 36a-37a,and a length of dry and cool veneers is extracted from the dryer.

The device according to this modified construction is especiallyadvantageous when, in spite of starting with a ribbed variety of wood,it is desired to obtain, for facilitating the subsequent treatments ofthe veneers, dry, cool and absolutely flat veneers.

In addition, the veneers thus treated pass out of the dryer withouthaving undergone any shrinkage and therefore without any fissure, splitor tear inherent with such shrinkage. They are, furthermore, veryflexible.

The joint action of the heating and cooling plates which has just beendescribed is applicable to the construction shown in FIG. 1.

The method of using the machine as above described may be varied asregards one or more possible lifting operations of the upper heatingplates 36 during the course of the drying position of the veneers of thecorresponding tier.

According to this modification, the upper heating plate 36 of a giventier occupying the bottom position, that is to say, the position fordrying the veneers may, instead of remaining in this lower positionduring the whole period of drying, be raised once or several timesduring this period of drying, the number of lifts and the exact cycle ofthese lifts being variable and previously adjustable in dependence ofthe purpose to be fulfilled.

In fact, by leaving these plates in the bottom position during theentire drying period, there is obtained a dry veneer which ispractically devoid of shrinking or as a maximum by about 1%. This is nota disadvantage for a number of given varieties of wood (poplars andgaboons for example) and for future applications of these veneers.

For other varieties of wood, micro-fissures then appear and may beincompatible with subsequent uses of these veneers with visible faces.This is the case for example with woods such as beech or ash and withmany veneers obtaines from sliced wood.

The utilization of lifting devices such as those which have been shownat 49 and 50 in H0. 2 of the drawings enables these lifting operationsof the heating plates (FIG. 2) to be carried out, which has theconsequence of removing these possible disadvantages by permittingshrinkage of the veneers while preserving furthermore all the propertieswhich form the advantage of this new machine, namely: flatness, veryshort drying time, large economy of total power consumption, very lowand uniform final moisture content. Shrinkage is furthermore effected inthis case without the appearance of any tearing on the complete strip ofveneers.

According to another modification, each of the heating plates 36 and 37may be constituted, not by a single plate formed by a thick steel sheetgrooved with channels for the circulation of the heating fluid, but withplates of this type of small size and arranged alongside each other soas to form a plate of large size, the construction of which, in a singlepiece, would be more costly.

It is envisaged that, according to another modification of theinvention. these heating plates could be constituted by tubes of squareor rectangular section inside which the heating fluid circulates andwhich are simply juxtaposed so as to reconstitute a heating plate. Theadvantages of such an improvement are to permit construction at a lowerproduction cost, to permit evacuabe arranged in the interior of eachsquare tube in order. to eliminate this difference in temperatures.These.

tubes may be juxtaposed according to the dimensions of the machine,either in the transverse direction or in the longitudinal direction.

According 'to a still further modification, the .conveyor belts may bemade of a special woven metallic fabric utilizing especially stainlesssteel wire or aluminum alloy wire for example,'so as to avoidanypossible reaction'between the sap of the green veneer and an ordiharysteel wire, which reactions might be the cause of stains on theseveneers.

Minor constructional details may be varied without departing from thescope of the subjoined claims.

I claim:

1. A machine for drying by contact veneers obtained from peeled orsliced wood, comprising in combination a frame, a plurality of pairs ofheating plates supported on the frame, the plates of each said pairbeing vertically superposed and said pairs being disposed one above theother, the upper heating plate of each pair being vertically movable onand relative to the frame toward and away from the lower heating plateof each pair, a plurality of endless flexible conveyor belts, meanspositioning a pair of runs of two said belts between each said pair ofheating plates to move between said plates veneers disposed between saidruns when said upper plates are raised and to retain said veneersmotionless between said plates when said upper plates are lowered intocontact with the upper of said runs, and a hood above said heatingplates for removing steam emitted by said veneers.

2. A machine as claimed in claim 1, at least one of said belts being ofwoven metal wire.

3. A machine as claimed in claim 1, said upper plates being mounted forvertical movement on said frame by means of cooperative stud and slotmeans carried on said frame and upper plates.

4. A machine as claimed in claim 1, there being two said endlessconveyor belts individual to each said pair of plates.

5. A machine as claimed in claim 1, there being two said conveyor beltscommon to a plurality of said pairs of plates and extending in zigzagfashion between said pairs of plates. I

6. A machine as claimed in claim 1 and cooling plates between which saidruns pass after passing between said heating plates.

1. A machine for drying by contact veneers obtained from peeled orsliced wood, comprising in combination a frame, a plurality of pairs ofheating plates supported on the frame, the plates of each said pairbeing vertically superposed and said pairs being disposed one above theother, the upper heating plate of each pair being vertically movable onand relative to the frame toward and away from the lower heating plateof each pair, a plurality of endless flexible conveyor belts, meanspositioning a pair of runs of two said belts between each said pair ofheating plates to move between said plates veneers disposed between saidruns when said upper plates are raised and to retain said veneersmotionless between said plates when said upper plates are lowered intocontact with the upper of said runs, and a hood above said heatingplates for removing steam emitted by said veneers.
 2. A machine asclaimed in claim 1, at least one of said belts being of woven metalwire.
 3. A machine as claimed in claim 1, said upper plates beingmounted for vertical movement on said frame by means of cooperative studand slot means carried on said frame and upper plates.
 4. A machine asclaimed in claim 1, there being two said endless conveyor beltsindividual to each said pair of plates.
 5. A machine as claimed in claim1, there being two said conveyor belts common to a plurality of saidpairs of plates and extending in zigzag fashion between said pairs ofplates.
 6. A machine as claimed in claim 1, and cooling plates betweenwhich said runs pass after passing between said heating plates.